Method of making electric-insulation bodies



Patented Oct. 26, 1926.

DANIEL MANSON SUTHERLAND, JR., OF TRENTON, NEW JERSEY.

mn'rnon or MAKING ELEc'rRIc-msULArIon BODIES.

No Drawing. Original application filed November 11, 1924, Serial No. 749,345. Divided and this application filed February 2, 1926. Serial No. 85,582.

My invention has for its object the economical production of insulatingqboards, sheets, and bodies of varied form, having a cellulose base, possessing high di-electric properties, and capable of bein readily machined, and finished in any deslred color or colors, or to simulate natural woods, stones, and the like.

Better to differentiate the present invention from the known prior art it may be stated that under existing practice, electrical insulation products having a cellulose base are prepared by making what is known .as hard or vulcanized fiber, zinc chloride, or sulphuric and nitric acids being used to dissolve the cellulose. Products thus made are laminated, and absorb water or moisture somewhat freely, for which reasons they are unsuitable for use where high dielectric or insulating effect is sought.

The prior. art discloses many combinations of binders with cellulose, designed to give, but not giving, the results which I have successfully attained by my new formula and procedure. Prior plans have involved the use of cellulose with various binders, such as asphalt, resin, and oil soaps, and the product has in some cases been given a surface coating of cellulose acetate; but as heretofore supplied, such compositions have been found deficient in dielectric properties, absorbent of moisture, and dif ficult to drill or machine, to finish in the various ways deemed desirable, or to engrave. i

For general uses, the material produced should be non-absorbent and devoid of tackiness, but highly dielectric, capable of being drilled, machined, engraved, or finished to present in color and surface an appearance substantially identical with those producible with or upon wood, stone and other substances, natural or artificial, and finally, these qualities should be stable and lasting.

Procedure under the present invention consists in combining cellulose and a suitable binder or. binders to produce a pulp; formingthe pulp into a sheet, board, block, or other body; drying the same; coating it with a suitable film, compressing or compacting' it' under heat and pressure; and

finally cooling itxwhile still under pressure. I

This process produces what is commonly known as the homogeneous board, and this Gilsonite v is the preferred formof the product. I can, however, produce on a cylinder wet machine, sheets, with laminations, which are, however, so closely compacted, or so firmly compressed by pressure and heat, followed by cooling under pressure, that such sheets closelyresemble in quality the homogeneous product.

high percentage or proportion of cellulose;

say 70% by weight of the composition or' mlxture, gives a product which does not drill cleanly or smoothly, has a high water absorption, and presents a surface strongly resembling enamel or patent leather, whereas a less glossy but smooth and even surface is generally deemed desirable. Materially lower percentage of cellulose, say 40% or thereabout, gives much better results.

Again, I have found that the resultant product is better when special care is taken to incorporate the binder with the cellulose in finely divided condition, the fibers being in such case more certainly and completely surrounded or. encompassed by the binder or binders.

The best composition and procedure that I have thus far developed through careful experimentation and practical use will now be stated, it being understood, however, that that reasonable variation in proportions and substitutions of equivalents can be made without materially or greatly affecting the result. A composition is formed comprising cellulose and a binder, preferably consisting of china wood oil soap or linseed oil soap,

or a mixture of the two, together with gil sonite. The following formula has given verysatisfactory results:

per cent.

Cellulose Oil soap Acaroid resin body when the pressure is discontinued.

The oil soaps are prepared by cooking, either in an open or in a closed vessel, china wood oil or linseed oil with caustic soda, until complete saponification is effected. The acaroid resin is dissolved in caustic soda and mixed with the oil soap or soaps in the proportion above stated.

The gilsonite is ground in Water until it is so fine that about 95% will pass through a 100 mesh screen, and after screening is mixed with the oil soap or soaps. The binder so prepared is then intimately mixed with the cellulose, and alum is used in quantity sufficient to neutralize the caustic soda and to precipitate the soap or soaps and acaroid resin in insoluble form upon the cellulose fibers. The gilsonite is in this manner held in suspension with the fibers, thus avoiding its subsequent loss during formation of the sheet, board, or other body.

The use of oil soaps and acaroid resin alone does not produce the desired results, since in the absence of gilsonite the product, after compression or compaction, will gradually swell when the pressure is with drawn, thus lessening its density and its water-resisting properties. Gilsonite is employed in preference to other and similar agents because it melts under the temperature and pressure which obtains during compression or compaction, and when subsequently cooled while the mass is still under pressure, it firmly cements together the cellulose fibers, and thus prevents in great degree the reswelling of the formed sheet or The surface of the formed body also re mains smooth for a longer period of time in consequence of the presence and action of the ilsonite.

T e use of oil soap improves the sanding or surfacing qualities of the finished body, and overcomes the tendency of gilsonite to gum abrasives, or to glaze and render ineffective abrading. and polishing wheels and surfaces.

The acaroid resin plays an important part in improving water resistance, or rendering the product non-absorbent, by causing the oil soaps to precipitate in a finely divided state, which would not happen in the absence of the acaroid resin.

A surface coating or film is applied to the article after it is formed and dried, in order to prevent the binders from adhering to the contacting surfaces of the hot press, dies, or molds in which the material 1sv compressed and fashioned, and for the further purpose of affording or permitting a high polish. I prefer for the surface film or coating, cellulose acetate or cellulose nitrate lacquers, which may be applied by dipping, spraying, or brushing. These lacquers can be colored before application by the use of suitable aniline dyes, soluble in alcohol, and may be applied in solid color, or to simulate different woods, stones, andother natural substances or materials.

When the composition is adequately compressed and compacted to produce a density of not less than 300 grains per cubic inch, and is cooled while 'still under pressure, an insulating material is produced which has high dielectric properties, good machining qualities. and a smooth and even surface, and which is non-absorbent or water repellant.

It will be seen from the foregoing descrip tion that I have produced a nicely'balanced composition of matter, in which each ingredient has and performs its own special and important office and function, combining, co-

operating, or reacting with or upon other in-' I gredlents 1n a manner to produce, under the described procedure, a highly efficient insulating material, of excellent appearance, and capable of being fashioned and finished without difficulty, and of being made to simulate very closely more expensive natural substances.

As above indicated, I have given the best formula known to me, but am aware that reasonable latitude is possible in the selection of ingredients possessing similar properties, and in the proportions of different ingredients employed. It is hence to be understood that I do not mean to limit myself to the use of the precise ingredients named, or to the exact proportions stated; but may vary each within reasonable limits. Thus, by way of example, a single oil soap or a plurality of such soaps may be used, the aggregate quantity being in each instance substantially that above roposed. So, too,

cellulose acetate or cellu ose nitrate may be mon and well known to those engaged in the manufacture of paper pulp and pulp products.

In an application filed in my name on the 4th day of August, 1924:, Serial No. 730,022, I have set forth the use of acarcold resin in a film or coating applied to the surface of insulating sheets, boards, and forms having a cellulose base, such film or coat ng serving to prevent adhesion of the lnsulat-ing body when subjected to heat and pressure, or subsequent to such compression under heat. Under the present plan, however, acaroid resin is incorporated in or is an 111- gredient of the binder, and is hence thoroughly commingled with the pulp mass; whereas under the prior application it was present only in the surface film or coating i ll This application is accordingly designed to claim and cover specifically such incorporation of the acaroid resin in the pulp mass.

This application is a division of one filed in my name on the 11th day of November, 1924, Serial No. 749,345, and is filed in compliance with oflicial requirement. Claims for the composition as such are retained in the parent application, and claims for the process of manufacturing products from such composition are contained in this divisional application.

What is claimed is 1. The herein described process of making dielectric bodies, which consists in combining cellulose and oil soap to produce a pulp; adding to the pulp a small percentage of acaroid resin and a relatively large percentage of gilsonite; fashioning the mass to desired form; drying the same; compressing and compacting the same under pressure and subject to heat; and thereafter cooling it While still subject to pressure.

2. The herein described process of making dielectric bodies, which consists in combining cellulose and oil soap to produce a pulp; adding to the pulp a small percentage of acaroid resin and a relatively large percentage of gilsonite; fashioning the mass to desired form; drying the same; coating the formed body with a cellulose lacquer; compressing the coated body in the presence of heat; and finally cooling the same While still under pressure.

In testimony whereof I have signed my name to this specification.

DANIEL MANSON SUTHERLAND, Jr. 

